This invention relates to an X-ray imaging apparatus which detects X rays transmitted through an object, and produces an image or measured value effective for medical diagnosis or industrial inspection of the object.
A typical example of the conventional X-ray imaging apparatus is a digital fluorographic apparatus. The image visually displayed by such an apparatus inevitably suffers from spatial distortion caused by the detecting system of the imaging apparatus. (The detecting system contains an image intensifier (I.I.) for converting a detected X-ray image into an optical image, and a television camera for converting the optical image into corresponding electrical signals.) In an extreme case, the displayed image loses to a significant degree and due to spatial distortion its geometrical analogy to the configuration of the object. In some cases, contiguous aspects of the object are X-ray imaged so as to provide a series of images of contiguous aspects of the object. These segmental image frames are then composed to provide a composite image for observation. However, should each frame contain a large degree of spatial distortion the composite image will, likewise, be characterized by distortion, to the extent of its being an unnatural representation. Similarly, if in the X-ray tomographic apparatus or an X-ray stereoscopic imaging apparatus, the spatial distortion is contained in the X-ray transmission images before reconstruction, the reconstructed tomographic or stereoscopic image will be quite different in configuration from the object.
The inspection results or geometrical measurements based on such distorted images inevitably contain errors, resulting in imprecise diagnosis and/or inspection.
A recent trend in this field is the attempt to apply the X-ray imaging apparatus, the X-ray tomographic apparatus, the X-ray stereoscopic imaging apparatus and the like to analysis of heart volume, as well as to the exact measurement of a target position of an object. Such exact measurement is required for, for example, the operation of destroying renal calculus by means of an impact wave, radiotherapy or hyperthermia. Naturally, the existence of spatial distortion and the errors ensuing therefrom in a case where nothing short of a very precise measurement is called for creates serious problems.